[libvirt] [PATCH] conf: Fix crash when src->hosts = NULL in virStorageFileBackendGlusterInit

[Luyao Huang]

https://bugzilla.redhat.com/show_bug.cgi?id=1162974

When do external snapshot for a gluster disk with no host name(ip) in
snapshot xml, libvirtd will crash. Because when node do not have a children
in virDomainStorageHostParse, libvirt will return 0, but donnot get hosts for
virStorageFileBackendGlusterInit.

snpahost.xml:

<domainsnapshot>
<name>snapshot_test</name>
<description>Snapshot Test</description>
<disks>
<disk name='vda' snapshot='external' type='network'>
<source protocol='gluster' name='gluster-vol1/gluster.img.snap'/>
</disk>
</disks>
</domainsnapshot>

Back trace:
virsh snapshot-create r6 snapshot.xml --disk-only

0  virStorageFileBackendGlusterInit (src=0x7fc760007ca0) at storage/storage_backend_gluster.c:577
1  0x00007fc76d678e22 in virStorageFileInitAs (src=0x7fc760007ca0, uid=uid at entry=4294967295, gid=gid at entry=4294967295) at storage/storage_driver.c:2547
2  0x00007fc76d678e9c in virStorageFileInit (src=<optimized out>) at storage/storage_driver.c:2567
3  0x00007fc76bc13f9c in qemuDomainSnapshotPrepareDiskExternal (reuse=false, active=true, snapdisk=0x7fc7600019b8, disk=0x7fc7641e4880, conn=0x7fc76426cc10)
    at qemu/qemu_driver.c:12995
4  qemuDomainSnapshotPrepare (flags=<synthetic pointer>, def=0x7fc760002570, vm=0x7fc76422b530, conn=0x7fc76426cc10) at qemu/qemu_driver.c:13156
5  qemuDomainSnapshotCreateXML (domain=0x7fc760001f30, xmlDesc=<optimized out>, flags=16) at qemu/qemu_driver.c:13896
6  0x00007fc782d4de4d in virDomainSnapshotCreateXML (domain=domain at entry=0x7fc760001f30,
    xmlDesc=0x7fc760001b80 "<domainsnapshot>\n<name>snapshot_test</name>\n<description>Snapshot Test</description>\n<disks>\n<disk name='vda' snapshot='external' type='network'>\n<source protocol='gluster' name='gluster-vol1/gluster."..., flags=16) at libvirt.c:18488
7  0x00007fc7837cb44c in remoteDispatchDomainSnapshotCreateXML (server=<optimized out>, msg=<optimized out>, ret=0x7fc760000a60, args=0x7fc760001f90, rerr=0x7fc77344dc80,

    client=<optimized out>) at remote_dispatch.h:8605

Signed-off-by: Luyao Huang <lhuang at redhat.com>
---
 src/conf/domain_conf.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/src/conf/domain_conf.c b/src/conf/domain_conf.c
index 2c65276..34c1c12 100644
--- a/src/conf/domain_conf.c
+++ b/src/conf/domain_conf.c
@@ -4150,7 +4150,12 @@ virDomainStorageHostParse(xmlNodePtr node,
 
     memset(&host, 0, sizeof(host));
 
-    child = node->children;
+    if ((child = node->children) == NULL) {
+        virReportError(VIR_ERR_XML_ERROR, "%s",
+                               _("Can not find a host in xml"));
+        goto cleanup;
+    }
+
     while (child != NULL) {
         if (child->type == XML_ELEMENT_NODE &&
             xmlStrEqual(child->name, BAD_CAST "host")) {
-- 
1.8.3.1